Childkiller
From The Vault
The Childkiller reputation is bestowed upon your character for killing a child, even if it's an accident. However if one of your party members does the deed instead, you won't be penalized for it.
If you have killed 3 or more children in Fallout or 2 or more children in Fallout 2 yourself, bounty hunters will eventually find you in random encounters. Their equipment depends on your level, ranging from Leather Jackets and Hunting Rifles to Power Armor and Avenger Miniguns.
You have killed children, the youth of the wasteland. This is considered to be a really bad thing. You evil, evil person.
Sometimes, you might not even know that you're killing a kid, because they're under the guise of a normal-looking person. For example, a teen still counts as a kid. An example of this is Myron: although in a general sense he's not a child, the game regards him as one.
[edit] Appearances
This reputation appears only in Fallout and Fallout 2. In Fallout 3, all children are unkillable without the "killable children" mod (although attacking them will still earn you the hostility of the locals), while in Fallout Tactics and Fallout: Brotherhood of Steel, there are no children at all.
Note that in Fallout 3 you have the possibility of killing 3 children: Harden Simms and Maggie when you blow up the town of Megaton; and Arthur Maxson when you blow up the Citadel (must have Broken Steel installed). As well Timmy Neusbaum "Dies" when the simulation failsafe is activated, though he is never seen gunned down by chinese solders it can be assumed that he meets the same fate as all the other people in the sim.

